- We propose to leverage a newly NIH-funded large, randomized, double-blind, placebo-controlled, 2x2 factorial trial of vitamin D (in the form of vitamin D3 [cholecalciferol]) and marine omega-3 fatty acid (eicosapentaenoic acid [EPA] + docosahexaenoic acid [DHA]) supplements to study effects upon autoimmune disease incidence, biomarkers of systemic inflammation, and chronic knee pain. Data from laboratory studies, epidemiologic research, and small prevention trials strongly suggest that these nutritional agents reduce the risk of autoimmune diseases, reduce levels of circulating pro-inflammatory cytokines, and decrease chronic joint pain. However, large primary prevention trials with adequate dosing in general populations (i.e., unselected for disease risk) have never been conducted. The growing enthusiasm for supplemental vitamin D and fish oils underscores the urgent need for their timely testing, before their use becomes so prevalent as to render participant recruitment and hypothesis testing impossible. The NIH-funded VITAL randomized controlled trial about to begin will involve 20,000 men aged e60 and women aged e65 recruited from a mailing to 1.2 million persons, including members of AARP (formerly known as the American Association of Retired Persons), and others. The mailing will contain a letter describing the trial, an informed consent form, and a questionnaire about past medical history, including autoimmune diseases and a screening assessment of chronic knee pain, as well as diet, medication and nutritional supplement use. At the end of a 3 month placebo run-in, those who remain willing and eligible, and who report having taken at least two-thirds of the pills, will be randomly assigned to one of four treatment groups for 5 years: vitamin D3 (1600 IU/d) and fish oil (EPA+DHA, 1 g/d); vitamin D3 and fish oil placebo; placebo vitamin D3 and fish oil; and placebo vitamin D3 and placebo fish oil. At yearly intervals, participants will receive a new supply of pills, and assessments of incident autoimmune diseases, knee pain, compliance and potential side effects. A physician endpoints committee will confirm all autoimmune disease endpoints by medical record review. We anticipate validation of 600 incident cases of autoimmune disease, giving us sufficient statistical power to assess supplement effects on disease incidence. Blood samples at baseline and in follow-up will be collected in a random subcohort of 2000 individuals and analyzed for changes in biomarkers of systemic inflammation: C-reactive protein, interleukin-6, and tumor necrosis factor-a. Approximately 2000 individuals with chronic, frequent knee pain will be followed with annual questionnaires, providing ample statistical power to evaluate the supplement effects upon chronic knee pain. To complete the pre-randomization assessment of knee pain, it is critically important that this ancillary study be undertaken in parallel to enrollment for the parent VITAL trial, beginning January 2010. Given the NIH-funded VITAL trial and our success with prior large mail-based trials and cohort studies, the proposed trial will furnish either definitive positive or informative null results regarding the central study hypotheses.